Many dyes are conventionally known and broadly classified into natural dyes and synthetic dyes. As the synthetic dyes, examples include, but are not limited to, aniline blue, fuchsine and methyl orange. Most of the synthetic dyes contain an aromatic or heterocyclic ring, and they are each an ionic compound (e.g., a water-soluble dye) or a nonionic compound (e.g., a disperse dye). Ionic dyes are classified into anionic dyes and cationic dyes.
A basic triarylmethane-based dye is a cationic dye and characterized by its color that is relatively deep and clear. Xanthene-based dyes such as rhodamine are characterized by strong fluorescence. Triarylmethane-based dyes and xanthene-based dyes are used in a wide variety of applications such as optical materials, since they have high transmittance.
However, depending on applications, dyes are insufficient in heat resistance or light resistance, and many studies have been made to increase their toughness.
As a color material with excellent heat resistance, the inventors of the present disclosure disclosed a specific color material containing two or more dye skeletons (e.g., Patent Literature 1).